1. Field of the Invention
The present invention relates to a sensor for wearing of brake as well as temperature thereof.
2. Description of the Prior Art
FIG. 1 shows configuration of the conventional wear sensor for a brake in sectional view and FIG. 2 shows detail of the sensor in an enlarged sectional view. As shown in FIG. 1, brake lining 1a and 1b are mounted on lining holder 2a and 2b, respectively in a frame 3'. The frame 3' has a piston 4, and a cylinder 3 containing the piston 4 is fixed to the lining holder 2a and pushes the lining 1a (the lining 1a and the holder 2a form a shoe) towards a rotor disc 6 when amount of brake fluid 5 increases in the cylinder 3 by means of known brake operation. Therefore, both surfaces of the rotor disc 6 are pinched between the brake lining 1a and 1b, respectively, thereby the rotation of the rotor disc 6 is braked by means of frictions between the faces of the rotor disc and the brake linings 1a and 1b. In the conventional brake wear sensor, a sensor 7 is provided buried in the brake lining 1 a in a manner that when the brake lining 1a wears to a predetermined position, tip of the sensor 7 becomes exposed and further wears out together with the brake lining 1a thereby making some change on the sensor.
Detail of one conventional example is shown in FIG. 2 wherein the sensor 7 comprises metal wire 8 of lateral V-letter shape buried in an insulator case 9, and both ends of wires are led out by means of lead wires 10. The end tip of the V-shaped metal wire 8 is disposed at a predetermined wear limit position B, at which the sensor should make a signal. Therefore, when the brake lining 1a goes on wearing, from an initial position A to the wear limit position B, the end tip of the metal wire 8 is cut out as the brake lining wears. According, the resistance between the lead wires 10, 10 become indinite from almost 0.OMEGA., thereby making a known subsequent circuit issue a worn out sensing signal.
The above-mentioned conventional wear sensor for a brake can sense only wearing of the brake lining, and as another problem, the sensor is unrestorably destroyed namely cut off with respect to the metal wire 8. Accordingly, the sensor 7 must be thrown away together with removal and thrown away of the worn brake lining 1a.
On the other hand, in recent years as automatic transmission becomes popular, when a novice driver continously uses foot brake, dangerous vapor locking of the brake system is liable to occur. This is because of undue temperature rise of brake fluid the brake fluid vaporises and generates foams in the brake fluid. In order to prevent such very dangerous vapor locking of a brake system, a sensor for detecting undue temperature rise of the brake fluid is recently waited for.